Integral image elements which use a lenticular lens sheet or a fly's eye lens sheet, and a three-dimensional integral image aligned with the sheet, so that a user can view the three-dimensional image without any special glasses or other equipment, are known. Such imaging elements and their construction, are described in "Three-Dimensional Imaging Techniques" by Takanori Okoshi, Academic Press, Inc., New York, 1976. Integral image elements having a lenticular lens sheet (that is, a sheet with a plurality of adjacent, parallel, elongated, and partially cylindrical lenses) are also described in the following Unites States patents: U.S. Pat. No. 5,391,254; U.S. Pat. No. 5,424,533; U.S. Pat. No. 5,241,608; U.S. Pat. No. 5,455,689; U.S. Pat. No. 5,276,478; U.S. Pat. No. 5,391,254; U.S. Pat. No. 5,424,533 and others. Integral image elements with lenticular lens sheets use interlaced vertical image slices which, in the case of a three-dimensional integral image, are aligned with the lenticules so that a three-dimensional image is viewable when the lenticules are vertically oriented with respect to a viewer's eyes. Similar integral image elements, such as described in U.S. Pat No. 3,268,238 and U.S. Pat. No. 3,538,632, can be used to convey a number of individual two-dimensional scenes (such as unrelated scenes or a sequence of scenes depicting motion) rather than one or more three-dimensional images.
Integral image elements using reflective layers behind the actual integral image itself, to enhance viewing of the integral image by reflected light, are also described in U.S. Pat. No. 3,751,258, U.S. Pat. No. 2,500,511, U.S. Pat. No. 2,039,648, U.S. Pat. No. 1,918,705 and GB 492,186.
In a typical method of assembling a lenticular type of integral image element, an original negative is exposed from stored digitized data of a composite lenticular image on a film writer. A suitable film writer is the Symbolic Sciences International Fire 1000 and the LVT Model 1620B, available from Light Valve Technology, a subsidiary of Eastman Kodak Company, Rochester, N.Y. More recently lower-priced printers, such as the Kodak XLS8650 Thermal Printer have been adapted to write these interlaced files. A suitable negative exposure technique is disclosed in U.S. Pat. No. 5,276,478. After photographic processing, the negative is printed, typically by a projection enlarger or by contact printing, onto a suitable film- or paper-based photographic print stock. After processing, the lenticular composite print is coated with adhesive, aligned with a lenticular lens sheet, and pressed against the lens sheet to permanently adhere to it in proper registration with the printed lenticular composite image. Alternatively, the integral image can be printed by exposing using a number of original images at different positions, through the front side (that is the side bearing the lenticular lenses) of a lenticular lens sheet onto a suitable photosensitive medium.
While the width of each set of image lines may be less than or equal to the width of a lenticule, and each may be centered under its corresponding lenticule, these conditions are not essential. For example, U.S. Pat. No. 5,278,608 and U.S. Pat. No. 5,276,478 describe methods in which the image sets become increasingly spaced from the centers of their respective lenticules moving from the center to the edges of the integral image element. What is typically required is that all of the lines from only a single image can be clearly viewed from an intended (that is, preselected) viewing position in front of the lenticular lens sheet. For individual integral image elements or for short runs (that is, only a small number of copies) of integral image elements, this has been accomplished in the known art by first accurately measuring the pitch of the lenticular lens sheet to be used. The pitch is a measure of the size of the lenticular lens elements. The spacing of the sets of image lines in the print of the integral composite image would then be selected by a suitable magnification of the original integral image (whether optically or mechanically during printing from a negative, or electronically before printing an integral image in a computer memory). Following selection of the magnification, the print would then be printed directly onto a separate substrate (such as photographic film) with the resulting print then being aligned adjacent the back side of the lenticular lens sheet.
Since each of the lenses of a lenticular lens sheet is dedicated to a single image set of interleaved image lines, it is important that the lenticules be rotationally and translationally positioned with the image line sets, so that each set is parallel and aligned with a corresponding lenticule. Schemes for rotationally and translationally positioning a print with an overlay are disclosed in U.S. Pat. No. 5,479,270. In the method of U.S. Pat. No. 5,479,270 one or more, usually black or white alignment lines, are present on the substrate carrying the image. However, particularly when alignment is to be accomplished manually by a user using their eye as a guide, it is necessary in the method of U.S. Pat. No. 5,479,270 for a user to carefully observe the black and white Moire patterns generated between the alignment lines and the lenticular lens sheet, to determine when the alignment is correct.
It would be desirable then, to provide a means by which relatively accurate alignment of image lines with corresponding lenticules can be readily obtained, and which means allows relatively easy alignment even if performed repeatedly by eye.